Experimental and Theoretical Study to Understand the Adsorption Process of p‐Anisidine and 4‐Nitroaniline for the Dissolution of C38 Carbon Steel in 1M HCl

Abstract

AbstractIn this work, we investigated the addition effect of two organic compounds namely; p‐anisidine (P1) and 4‐nitroaniline (P2) against corrosion of C38 steel in an acidic medium HCl 1 M. We opted for these inhibitors belonging to the aniline family which is characterized by their solubility, their low cost, and their use as corrosion inhibitors in acidic environments. The concentration effect of the two products P1 and P2 either by stationary or by transiency measurements appears a significant decrease in the corrosion rate, and that the inhibition efficiency IE% reaches a value of 88.55 % and 84 % for a concentration of 1 mM respectively of P1 and P2. The thermodynamic parameters taken from the electrochemical impedance curves indicate that the tested inhibitors are adsorbed on the metal surface by a mixed mechanism (physical‐chemisorption), because the free adsorption energy of P1 and P2 is respectively equal to −38.02 Kj.mol−1 and −37.56 Kj.mol−1, and they are subjected to the Langmuir isotherm. The temperature effect lets to determine the activation energy (Ea) from the Arrhenius equation; however, the values of Ea indicate the adsorption of organic compounds on the metal surface. Scanning electron microscopy (SEM) suggested that the products tested could effectively block acid attack on metal surfaces. In parallel to experimental approach, theoretical one based on theoretical function density (DFT) calculation and Monte Carlo (MC) simulation is considered to investigate in depth the inhibition behavior of studied compounds.